Isotropic Radiation Pattern Research Articles

Research on Quasi-isotropic Radiation of Small Circular Arc Antenna

The radiation characteristics of circular arc antennas are studied by applying the method of moments (MoM) to solve the electric field integral equation (EFIE). Based on the triangular current distribution of small circular arc antennas, the analytical expression of radiation fields of circular arc antennas is derived. It is found that the circular arc antenna is equivalent to a superposition of an electric dipole and a magnetic dipole, resulting in near isotropic radiation pattern. Finally, both MoM and CST simulations show that the small arc antenna can realize the near isotropic radiation pattern.

Measurements of multijet event isotropies using optimal transport with the ATLAS detector

A measurement of novel event shapes quantifying the isotropy of collider events is performed in 140 fb−1 of proton-proton collisions with s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV centre-of-mass energy recorded with the ATLAS detector at CERN’s Large Hadron Collider. These event shapes are defined as the Wasserstein distance between collider events and isotropic reference geometries. This distance is evaluated by solving optimal transport problems, using the ‘Energy-Mover’s Distance’. Isotropic references with cylindrical and circular symmetries are studied, to probe the symmetries of interest at hadron colliders. The novel event-shape observables defined in this way are infrared- and collinear-safe, have improved dynamic range and have greater sensitivity to isotropic radiation patterns than other event shapes. The measured event-shape variables are corrected for detector effects, and presented in inclusive bins of jet multiplicity and the scalar sum of the two leading jets’ transverse momenta. The measured distributions are provided as inputs to future Monte Carlo tuning campaigns and other studies probing fundamental properties of QCD and the production of hadronic final states up to the TeV-scale.

Wideband differential‐fed metasurface antenna array using characteristic mode analysis

AbstractA wideband differential‐fed (DF) metasurface (MTS) antenna array is proposed in this letter. As the element of the proposed array, a nonuniform MTS is designed step by step using characteristic mode analysis. In the first step, a 2 × 2 rectangular patch‐based MTS is investigated. We observe that its two fundamental modes exhibit even/odd symmetric current distributions, which can be regarded as a pair of c/π modes. Unlike c mode, π mode features nonbroadside radiation, which can be reshaped by modifying MTS to an asymmetric configuration in the second step. In the last step, a direct DF method is adopted to excite c/π modes and suppress other unwanted modes for wideband performance. The optimal DF positions are quantitatively predicted by calculating the impendence bandwidth of MTS fed by virtual probes. Moreover, to further increase the gain and improve the symmetry of radiation patterns, two proposed elements are integrated into a linear array. Finally, the proposed antenna array is fabricated and measured. The measured impedance bandwidth is 22.2% (6–7.5 GHz) with broadside radiation, stable gains varying from 8.5 to 11.3 dBi, and a front‐to‐back ratio better than 19 dB.

A Miniaturized Arc Shaped Near Isotropic Self-Complementary Antenna for Spectrum Sensing Applications

This paper presents the design of an arc-shaped near-isotropic self-complementary antenna for spectrum sensing application. An arc-shaped dipole with horizontal and vertical arms is used to achieve a near isotropic radiation pattern. The radiation pattern improved by adjusting the horizontal and vertical arm lengths. Simulated and experimental results show that the proposed antenna has an impedance bandwidth of 146% (2.4-18.4 GHz) for VSWR ≤ 2 with a good radiation pattern. In order to quantify the antenna performance, antenna gain variation, bandwidth, efficiency, and size have been compared with previously reported designs. It is shown that the proposed arc-shaped antenna can achieve nearly isotropic radiation patterns with a maximum radiation efficiency of 92%. The isotropic performance of the antenna has been characterized by observing the radiation pattern and solid angle. The FR4 substrate is used as a dielectric with relative permittivity 4.4 and loss tangent of 0.02. (εr = 4.4, h = 1.6 mm) The simulated and measured results are in good comparison, and the proposed design is a suitable candidate for spectrum sensing.

Experimental Connectivity Analysis for Drones in Greenhouses

This study aims to explore the communication capabilities for video crucial applications of two commercial drones—the Parrot AR.Drone 2.0 and the Parrot Anafi—in a greenhouse environment. Experiments were conducted on Received Signal Strength (RSS), Round-Trip Time (RTT) and the throughput on 802.11n at the 2.4 GHz network. From the experiments, it was found that none of the UAVs have an isotropic radiation pattern. Indoor measurements close to the roof and the ground were more prone to signal degradation. Even though the RTT of the Parrot Anafi was higher than that of the AR.Drone 2.0, the Anafi in almost all cases managed to achieve higher throughput and lower path loss, proving its superiority for video application. In addition, the maximum distance that the Parrot Anafi could fly in the greenhouse without any video quality loss was 110 m, while the AR.Drone 2.0 was hardly able to reach 30 m. Finally, the effect of the propellers has an insignificant impact on the UAV connection characteristics in all tested scenarios.

Highly Integrated Multifunctional Antenna for Global Navigation Satellite System

This communication proposes a new highly integrated multifunctional global navigation satellite system (GNSS) antenna used for navigation or surveying high-precision area, the fourth-generation (4G) mobile communication, and short-distance wireless communication. The antenna consists of four elements, saying: 1) a low-profile navigation element on one substrate covering all the GNSS bands and 2) two long-term evolution multiple-input–multiple-output (LTE-MIMO) elements and one Wi-Fi element uniformly distributed on the edge of the substrate. This symmetrical configuration ensures the navigation element’s low axial ratio (AR) and radiation pattern symmetry, as well as navigation accuracy. In addition, to enhance the isolation between the GNSS element and other three elements under high integration, these three elements are designed to avoid resonating within the GNSS bands. The measured peak gains of the GNSS element are 6.0 dBi from 1.16 to 1.28 GHz and 6.5 dBi from 1.52 to 1.62 GHz. The −6 dB impedance bandwidth of the LTE-MIMO elements can cover 840–960, 1800–2200, and 2500–2700 MHz. The distance communication of the Wi-Fi element is 80 m. The experimental results indicate that the proposed multifunctional antenna features low profile, high integration, and wideband, implying potential application in the multifunctional satellite navigation system.

Directive properties of radiating source systems in massive electromagnetism

We investigate the problem of electromagnetic radiation in massive electromagnetism with focus on the directive radiation characteristics of Proca antennas (sources embedded into Proca metamaterial domains.) It is theoretically demonstrated that the recently proposed nonlocal Proca metamaterial implies the existence of point nonlocal sources possessing a perfectly isotropic radiation pattern. Based on rigorous analysis, we derive exact expressions for the directive radiation patterns of arbitrary discrete distributions of Proca source systems, i.e., radiating arrays emitting massive photons. Examples of linear discrete Proca arrays are given and comparison with massless photon radiation sources is provided.

Improving the Sidelobe Level, Return Loss and Bandwidth of Notch-Loaded TM30 Mode Patch via Fractal-Slot

This paper presents a method for sidelobe level (SLL) reduction, return loss improvement, and bandwidth enhancement in notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode rectangular patch antennas. In this method, a fractal-slot is introduced in the center of notch-loaded patch to remove the unwanted out-of-phase current regions. It is shown that a combination of the fractal-slot and notch loading technique can achieve significant improvement in SLL, return loss, and bandwidth of notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode without compromising gain or symmetry of radiation patterns. Moreover, the method also gives an additional degree of freedom to improve the impedance matching without changing the feed location. A prototype of the antenna is fabricated to verify the proposed method. The proposed antenna shows a measured gain of 13 dBi with a low SLL of −16 dB. Furthermore, it shows symmetrical patterns in both planes with cross-polarization (X-pol) levels of less than 35 dB. An under-sampled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> array of the proposed antenna is also presented by utilizing its low SLL property to simplify the complexity of feed networks in high gain array antennas. The array offers the same directivity and SLL as that of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times 8$ </tex-math></inline-formula> array of fundamental mode rectangular patch elements in the same area.

A Dual Slant-Polarized Cylindrical Array of Tightly Coupled Dipole Antennas

This study proposes a design of a low-profile ultra wide-band cylindrical antenna array with plus/minus 45-degree dual polarization. The proposed compact cylindrical antenna array produces an omnidirectional radiation pattern in the azimuth plane to cover all directions. It consists of <inline-formula> <tex-math notation="LaTeX">$20\times 4$ </tex-math></inline-formula> dual-polarized elements within a diameter of 131 mm and a height of 116 mm. The array elements are tightly coupled slant-polarized wideband dipole antennas, and hence, rotational symmetry of radiation patterns in the horizontal plane is achieved for the two orthogonal polarizations. Furthermore, a metasurface structure has been designed and placed over the interconnected array elements to achieve ultrawideband capabilities. The proposed array provides less than &#x2212;10 dB reflection coefficient over a frequency band between 1.7 GHz and 5.9 GHz. The cross-polarization discrimination (XPD) is 15 dB at boresight in the azimuth plane. The electromagnetic characteristics of the cylindrical array and its corresponding planar array before bending have been evaluated and compared via simulations, and verified by measurements. The compact size, lightweight, and printable design of the proposed antenna array enable low-cost manufacturing and ease of installation. The proposed array design overcomes many challenges encountered in wide-band MIMO systems by covering the entire sub-6 GHz band while providing wide 360-degree coverage in the azimuth plane, hence, supporting multibeam applications.

Folded microstrip antenna with isotropic radiation pattern

AbstractIn contrast to existing antennas with polarization and directional characteristics, we propose a novel isotropic antenna that provides equivalent vertical and horizontal polarization in all directions. The final design was guided by simulations, with the performance characteristics of the fabricated antenna verified experimentally. In the proposed antenna, two λ/4 folded microstrip antennas were integrated into one antenna in a “+” shape to generate the isotropic radiation pattern, with the input impedance matched to the feeding position. The resonant frequency, horizontal width, radiation pattern, and axis ratio were adjusted by changing the length of the microstrip line. Both simulations and experiments confirmed that the radiation patterns of vertical and horizontal polarization on each plane show the characteristics of an isotropic antenna with nondirectional radiation pattern.

Proca Metamaterials, Massive Electromagnetism, and Spatial Dispersion

AbstractA class of electromagnetic metamaterials (MTMs) is investigated, which the author dubs Proca MTMs, constituting a medium behaving like a “relativistic material” for potential use in electromagnetic applications. This work is motivated by numerous previous results on particular structures such as plasma, waveguides, photonic crystals, magnetic materials, where it has been observed that photons may acquire mass in some dispersive domains. In this approach, it is rigorously proved using a field‐theoretic approach that Maxwell theory inside certain classes of nonlocal (spatially‐dispersive) metamaterials is equivalent to Proca theory in vacuum, where in the latter photons acquire a nonzero mass (massive electromagnetism.) An explicit closed‐form general expression for the Proca MTM dielectric function is given. It turns out that the key to the operation of Proca MTM is spatial dispersion, and hence Proca MTMs represent an important example of the more general family of nonlocal MTMs. The author's analysis involves multiphysics aspects, utilizing concepts and methods taken from classical electromagnetism, special relativity, quantum theory, electromagnetic materials, and antenna theory. Extensive discussion of the physics, computational methods, and design parameters of Proca MTMs is provided to further understand the nature of massive electromagnetism in nonlocal (spatially‐dispersive) MTMs. As a concrete application, the main ingredients of Proca antennas are developed as an example of the emerging technology of nonlocal antennas, where the author establishes that a single Proca dipole possesses a perfect isotropic radiation pattern, a noteworthy departure from conventional local antennas (radiators in vacuum and temporally dispersive media) where such radiation characteristics is impossible.

Low-Cost Distributed Acoustic Sensor Network for Real-Time Urban Sound Monitoring

Continuous exposure to urban noise has been found to be one of the major threats to citizens’ health. In this regard, several organizations are devoting huge efforts to designing new in-field systems to identify the acoustic sources of these threats to protect those citizens at risk. Typically, these prototype systems are composed of expensive components that limit their large-scale deployment and thus reduce the scope of their measurements. This paper aims to present a highly scalable low-cost distributed infrastructure that features a ubiquitous acoustic sensor network to monitor urban sounds. It takes advantage of (1) low-cost microphones deployed in a redundant topology to improve their individual performance when identifying the sound source, (2) a deep-learning algorithm for sound recognition, (3) a distributed data-processing middleware to reach consensus on the sound identification, and (4) a custom planar antenna with an almost isotropic radiation pattern for the proper node communication. This enables practitioners to acoustically populate urban spaces and provide a reliable view of noises occurring in real time. The city of Barcelona (Spain) and the UrbanSound8K dataset have been selected to analytically validate the proposed approach. Results obtained in laboratory tests endorse the feasibility of this proposal.

Design of miniaturized super wideband printed monopole antenna operating from 0.7 to 18.5 GHz

A design of compact Super-Wide Band (SWB) antenna with enhanced- bandwidth for wireless application is presented in this article. The proposed structure has fusion geometry of circular, square and trapezoidal slots on the rectangular radiator with a defected ground plane being used to enhance the VSWR bandwidth. Rectangular and trapezoidal-shaped slots are added in the ground plane to enhance the impedance bandwidth towards the lower cut off frequency. The proposed antenna has VSWR ≤ 2, average gain of 4.68 dBi, radiation efficiency of ≥ 83, fractional bandwidth (FBW) of 185.41%, and good pattern characteristics are achieved throughout the band. Moreover, the proposed SWB antenna is implemented in two ports multiple-input and multiple-output (MIMO)/diversity antenna. The diversified performances of MIMO antenna are calculated and it is observed that the proposed system has an isotropic radiation pattern. Four different configurations of MIMO antennas are designed and good isolation is achieved from port-to-port. The fabricated antenna has good agreement between simulated and measured results. The proposed antenna finds its applications in a wide range of UWB, K and Ku band portable devices.

E/H-평면의 방사 패턴 대칭성이 개선된 이중슬롯 비발디 안테나의 설계

E/H-평면의 방사 패턴 대칭성이 개선된 이중슬롯 비발디 안테나의 설계

The Role of Feed Perturbation in the Design of Microstrip-fed Cylindrical Dielectric Resonator Antennas

In this paper, the role of feed perturbation in the design of a cylindrical dielectric resonator antenna (DRA) for maximum modal purity is investigated both numerically and experimentally. Modal purity is indicated by the purity of the far-field radiation which can be quantified by the radiation pattern symmetry and the cross-polarized radiation. To demonstrate the feed perturbation effect, a microstrip line proximity coupled to a cylindrical dielectric resonator exciting its lowest order broadside radiating mode is used. It is identified that the feed perturbation introduces higher order fields of TM01δ and HEM21δ types of the DRA to disturb the modal purity of the desired mode. Results suggest that optimum DRA design should consider the feed perturbation effects also in addition to the common performance parameters such as impedance matching, bandwidth and gain.

Testing the Radiation Pattern of Meteor Radio Afterglow

AbstractRadio emission from meteors or meteor radio afterglows (MRAs) was first detected using the all‐sky imaging capabilities of the first station of the Long Wavelength Array (LWA1). In this work, we use the recently commissioned LWA Sevilleta (LWA‐SV) station along with the LWA1 to carry out coordinated observations. The combined all‐sky observations with LWA1 and LWA‐SV have coobserved 32 MRAs and 21 transmitter reflections from meteors (meteor scatter events), which are believed to be specular reflections from overdense trails. The flux density of the events observed by each station was measured from the all‐sky images. Triangulating the angular direction of events from each station gave the physical location and the distance of the event to each station. The luminosity of the events in each station was calculated using the flux distance relation for an isotropic source. The luminosity distribution for MRAs and meteor scatter events observed by each station shows a clear distinction between these two types of events as the ratio of luminosities is closer to unity for MRAs than the meteor scatter events. Furthermore, we find that MRAs follow an isotropic radiation pattern. This suggests, either a complete incoherent emission mechanism or an incoherent addition of coherently emitting small regions within the meteor trail.

Low-Profile Circularly Polarized Array With Gain Enhancement and RCS Reduction Using Polarization Conversion EBG Structures

A planar antenna array based on checkerboard polarization conversion electromagnetic band-gap (CPC EBG) structures with wideband circular polarization and low radar cross section (RCS) is presented. The array is formed by $2\times 2$ circularly polarized (CP) element antennas fed with a sequential feeding network. On the one hand, CP radiation is obtained due to the polarization conversion characteristic of the metamaterials. A sequentially rotated feeding network is employed for wide operating bandwidth, polarization purity, and radiation pattern symmetry. The measured results show that the array has a wide usable bandwidth of 18.4%, the common part of an impedance bandwidth of 37.3% (4.80–7.00 GHz), a 3 dB axial ratio (AR) bandwidth of 22.5% (5.00–6.27 GHz), and a 3 dB gain bandwidth of 18.4% (4.94–5.94 GHz). On the other hand, the checkerboard arrangement of the EBG structure generates both an in-band and a partial out-band RCS reduction under normal incidence for both $x$ - and $y$ -polarizations. Besides, the proposed array achieves a significant gain enhancement compared to the traditional slot array. The experimental and simulated results are in good agreement.

Three‐dimensional circular patch antenna under TM 02 mode with improved impedance matching

A circular patch antenna under TM 02 mode with improved impedance matching is proposed by adopting 3D architecture. It is known that the TM 02 mode of circular patch can generate omnidirectional radiation, but its input resistance reaches maximum at centre point. In this context, impedance matching is difficult to be achieved and the feeding probe is often supposed to be placed a distance away from the centre, inevitably destroying the symmetry of radiation pattern. Without introducing pins or slots, a direct strategy is here employed where the circular patch is folded to form a concave at its centre. It is found that the input resistance can be effectively reduced with increasing depth of concave since the described concave serves as vertical electric wall in cavity and weakens the electric field in the region between centre and ground. By using electroplate technology based on plastics, a 3D antenna prototype is fabricated and measured to validate the proposed methodology.

A W-Shaped Antenna With Spatial Polarization Variation for Direction Finding

A compact impedance-matched W-shaped antenna is presented that can radiate a perfect circular polarization (CP) at its boresight and distinct polarization states at different propagating directions in the far-field. The antenna structure consists of a horizontal dipole, a vertical dipole, and two elliptical loops connecting the adjacent arms of the dipole elements. The arc length and geometry of the loops are designed to produce the perfect CP at the boresight of the antenna. Using a single feed point, the antenna has an isotropic radiation pattern and is capable of producing distinct polarization states in different directions except for the plane of the antenna. Also, the symmetrical polarization characteristics with respect to the axes of the antenna symmetry are shown in the same propagating direction. This ambiguity of polarization can be resolved by using a pair of the proposed antennas operating at slightly different frequencies as a transmitter and triad dipoles to realize an azimuth-polar direction finding system. To demonstrate the validity of the antenna design, an antenna structure operating at 2.58 GHz is fabricated over a ground plane and measured. The measured radiation pattern shows the perfect CP at the boresight and 6.2% for the 3 dB axial ratio bandwidth.

Flying Ad Hoc Networks: A New Domain for Network Communications.

The advent of flying ad hoc networks (FANETs) has opened an opportunity to create new added-value services. Even though it is clear that these networks share common features with its predecessors, e.g., with mobile ad hoc networks and with vehicular ad hoc networks, there are several unique characteristics that make FANETs different. These distinctive features impose a series of guidelines to be considered for its successful deployment. Particularly, the use of FANETs for telecommunication services presents demanding challenges in terms of quality of service, energy efficiency, scalability, and adaptability. The proper use of models in research activities will undoubtedly assist to solve those challenges. Therefore, in this paper, we review mobility, positioning, and propagation models proposed for FANETs in the related scientific literature. A common limitation that affects these three topics is the lack of studies evaluating the influence that the unmanned aerial vehicles (UAV) may have in the on-board/embedded communication devices, usually just assuming isotropic or omnidirectional radiation patterns. For this reason, we also investigate in this work the radiation pattern of an 802.11 n/ac (WiFi) device embedded in a UAV working on both the 2.4 and 5 GHz bands. Our findings show that the impact of the UAV is not negligible, representing up to a 10 dB drop for some angles of the communication links.